Question

Sum of measure of exterior angle and interior angle of a vertex on a polyon is

• A. ${90}^o$
• B. ${180}^o$
• C. ${270}^o$
• D. ${360}^o$

Answer 1

The correct option is B ${180}^o$

Interior angles are formed by adjacent sides of the polygon at the vertices while exterior angles are formed by the sides of the polygon when an adjacent side is extended.

Exterior angle and the corresponding interior angle form a linear pair.
The exterior angle $\angle B^{/}BC$ is formed by extending the side BA.

$B^{/}BA$ is a straight line.
$\therefore \angle B^{/}BC+\angle CBA=\angle B^{/}BA={180}^o$